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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

ADVANCED MATERIALS AND FABRICATION METHODS FOR FLAME RETARDANT APPLICATIONS

Wojtal, Patrick January 2016 (has links)
Investigation of flame retardant materials (FRM) identified materials as effective substitutes for halogenated FRM. Many promising materials were tested such as hydrotalcite-type Al–Mg–Zr complex hydroxide, huntite, aluminum hydroxide, hydrotalcite, magnesium carbonate hydroxide pentahydrate, magnesium sulfate heptahydrate, magnesium phosphate hydrate, magnesium chloride hexahydrate, sodium metasilicate pentahydrate, XZO 2022 (Mg3Al) and halloysite. Electrophoretic deposition (EPD) manufacturing technique has been developed for the fabrication of coatings containing the most promising FRM candidates. Identifying charging and dispersion agents, such as poly(4-vinylpyridine-co-butyl methacrylate), humic acid, 2,2′- biquinoline-4,4′-dicarboxylic acid, quaternized hydroxyethylcellulose ethoxylate, 3- phosphonopropionic acid, 16-phosphonohexadecanoic acid, octadecylphosphonic acid, celestine blue, chitosan, to facilitate EPD was of great importance for successful deposition of composite FRM films. The films were investigated using scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, thermogravimetric and differential thermal analysis, as well as Fourier Transform Infrared and Ultraviolet-Visible spectroscopy. / Thesis / Master of Science (MSc) / Technology is expanding, as is our understanding of the environmental and health impacts of chemicals. New flame retardant materials (FRM) must be developed to help protect against fire hazards in increasingly complex products, but care must be taken to avoid implementing dangerous chemicals. This work identifies new FRM which can be efficient replacements for widely used, but toxic FRM. FRM can be applied as a coating cheaply, quickly, and evenly onto substrates of even a complex shape. Techniques and additive chemicals are suggested to create advanced FRM coatings
2

The affinity labelling of gibberellin hydroxylases

Brown, Robert Gareth Sumser January 1995 (has links)
No description available.
3

Applications of ventilation-controlled oxygen depletion calorimetry in fire research

Jowett, Paul Andrew January 1997 (has links)
No description available.
4

Sintesi, caracterització i entrecreuament de noves reïnes epoxi fosforades retardants de la flama

Ribera Llonc, Gemma 04 November 2004 (has links)
Los compuestos organofosforados han demostrado ser buenos retardantes para materiales con un elevado contenido en oxigeno, como es el caso de las resinas epoxi, además de generar menos gases tóxicos y humo que los compuestos halogenados. Así, se ha descrito como la introducción de óxidos de fosfina, tanto en la cadena de resina epoxi como en el agente de curado, les confiere buenas propiedades retardantes a la llama ya que actúan a través de un mecanismo de intumescencia, formando una capa aislante que constituye una barrera física y térmica a la combustión. Los objetivos de este trabajo son la síntesis y el entrecruzamiento de nuevas resinas epoxi fosforadas, y el estudio de sus propiedades térmicas, mecánicas i de retardáncia a la llama.Una via de obtención de resinas epoxi fosforadas es la síntesis de prepolímeros fosforados derivados de IHPO i DGEBA así como de un nuevo diglicidilo alifático, el HEDGE, sin embargo en este caso a medida que el HEDGE reaccionaba con el IHPO formando el prepolímero, al mismo tiempo se producía su homopolimerización. De la misma forma que en el caso del IHPO, se intentó alargar la cadena del Fyrol 6 mediante su reacción con DGEBA o con EPC en preséncia de TBAH, pero no se produjo la reacción esperada lo que hizo que se descartara esta via de síntesis de resinas epoxi fosforadas.Una via alternativa es la síntesis de diglicidilos fosforados por lo que se hizo reaccionar el IHPO con EPC en medio básico y en preséncia de un catalizador de transferéncia de fase. Este nuevo diglicidilo experimenta reacciones de isomerización y descomposición a temperaturas elevadas, junto con la reacción de homopolimerización térmica, lo que hace necesario el uso de un catalizador en la reacción de curado, ya sea catiónico o aniónico.Otra forma de introducir fósforo en la resina epoxi es curando compuestos diglicidílicos con agentes de curado que contengan el grupo P=O. Por esta razón se sintetizaron dos aminas fosforadas, el BAMPO, una diamina que incorpora el grupo P=O unido directamente a dos anillos aromáticos, y la 2DOPO-A, una diamina que incorpora dos moléculas de DOPO en su estructura. También se sintetizó el DAPPO, una diamida donde el nitrógeno tiene una unión directa con el átomo de fósforo, que se decidió no incluir en el estudio de las reacciones de curado con los diglicidilos sintetizados, porqué producía grados de curados bajos.Una vez obtenidos los compuestos fosforados se estudió la reacción de curado del DGEBA con cinco aminas primárias (HMDA, DAT, DDM, BAMPO y 2DOPO-A) y se comparó con los resultados obtenidos del curado del IHPO-Gly y el HEDGE con estas cinco aminas. De este estudio se desprende que los tres glicidilos presentan temperaturas de reacción similares, sin que se pueda establecer ninguna relación con la estructura química del glicidilo, a diferéncia de las Tg obtenidas, que se ven afectadas tanto por la estructura del diglicidilo como del agente de curado. También se realizaron mezclas de IHPO-Gly con HEDGE o DGEBA, en proporciones que contenian el 1, el 3, el 5 y el 7% de P para poder ver la influéncia de la cantidad de fósforo presente en las resinas finales, que se curaron con DAT y con DDM. En los sistemas IHPO-Gly/HEDGE se observó un augmento de la Tg con la preséncia de la unidad P=O, mientras que en los sistemas IHPO-Gly/DGEBA la variación de la Tg se asocia a la preséncia de la estructura aromática.Mediante la técnica del DMTA se pudieron observar las Tg de los materiales obtenidos, así como una relajación hacia -50 provocada por los segmentos de los anillos oxiránicos abiertos, en todos los casos. Mediante la técnica del TGA se pudo determinar que la preséncia de fósforo inhibe la degradación oxidativa del resto carbonado en atmosfera de aire, produciendo la formación de un residuo intumescente que protege el material del fuego. Finalmente, mediante la aplicación del Test UL-94 de quemado vertical, todos los materiales fueron clasificados como V-0. / The organophosphorus compounds have demonstrated to be good flame retardants for materials with a high content in oxygen, since it is the case of the epoxy resins, beside less toxic gases and smoke generated that the halogen compounds. This way, it has been described as the introduction of phosphine oxides, so much in the chain of epoxy resin as in the curing agent, awards good properties of flame retardant since they act across a mechanism of lump, forming an insulating cap that constitutes a physical and thermal barrier to the combustion. The aims of this work are the synthesis and the crosslinking of new epoxy resins containing phosphorus, and the study of his thermal, mechanical and flame retardant properties.A route of obtaining epoxy resin containing phosphorus is the synthesis of phosphorus containing prepolymers derivatives of IHPO i DGEBA as well as of a new aliphatic diglycidyl, the HEDGE, nevertheless in this case as the HEDGE was reacting with the IHPO forming the prepolymer, at the same time his homopolymerization was taking place. In the same way as in case of the IHPO, the chain of the Fyrol 6 tried to lengthen by means of his reaction with DGEBA or with EPC, but the awaited reaction did not produce to itself what did that there was discarded this route of synthesis of phosphorus containing epoxy resins.An alternative route is the synthesis of phosphorus containing diglycidyl for what the IHPO made be reacted by EPC in basic way. This new diglycidyl experiences reactions of isomerization and decomposition to high temperatures, together with the reaction of thermal homopolymerization, which makes the use of a catalyst necessary in the reaction of treated, already is cationic or anionic.Another way of introducing phosphorus in the epoxy resin is treating diglycidyl compounds with curing agents that contain the group P=O. For this reason two phosphine oxide containing amino groups were synthesized, the BAMPO, a diamina that incorporates the group P=O joined directly two aromatic rings, and the 2DOPO-A, one diamina that incorporates two DOPO's molecules in his structure. Also the DAPPO was synthesized, a diamida where the nitrogen has a direct union with the atom of phosphorus, which was decided to include in the study of the reactions of treated by the synthesized diglycidyl, because was producing low degrees of crosslinking.Once obtained the phosphorus compounds was studied of the curing reaction of the DGEBA by five curing agents (HMDA, DAT, DDM, BAMPO and 2DOPO-A) and was compared with the results obtained of curing of the IHPO-Gly and the HEDGE with these five aminas. Of this study it is clear that the three diglycidyl present similar temperatures of reaction, without it could establish no relation with the chemical structure of the diglycidyl, to different of the obtained Tg, which meet affected so much for the structure of the diglycidyl as of the curing agent. Also IHPO-Gly's mixtures realized with HEDGE or DGEBA, in proportions that contain the 1, 3, 5 and 7 % of P to be able to see the influence of the quantity of present phosphorus in the final resins, which they react with DAT and with DDM. In the systems IHPO-Gly/HEDGE an increase of the Tg was observed by the presence of the unit P=O, whereas in the systems IHPO-Gly/DGEBA the variation of the Tg is associated with the presence of the aromatic structure.By means of the technology of the DMTA could be observed the Tg of the obtained materials, as well as an easing towards-50 provoked by the segments of the oxyranic rings opened, in all the cases. By means of the technology of the TGA it was possible to determine that the presence of phosphorus disables the oxidative degradation of the carbonated rest in air atmosphere, producing the formation of a intumescent residue that protects the material of the fire. Finally, by means of the application of the Test UL-94 of vertical burned, all the materials were classified like V-0.
5

Distribution of Polybrominated Diphenyl Ethers Among Demographic Categories

Merilis, Giorvanni 07 July 2017 (has links)
Polybrominated Diphenyl Ethers (PBDEs) are flame retardants widely used within the United States in various products such as plastics, electronics, textiles and furniture. With an increase in production and usage, PBDEs have recently emerged as a contaminant of concern. Due to their chemical structure, PBDEs have the propensity to bioaccumulate in mammals. In fact, elevated PBDE concentrations have been recorded in human breast milk. Due to the potential widespread exposure to PBDEs, this study investigates human blood concentrations of PBDEs generated through the 2003-2004 National Health and Nutrition Examination Survey. Through the use of statistical modeling, a comparison of mean PBDE concentrations in ng/g lipid is conducted based on age, gender and ethnicity. From a sample of 2337 individuals, the average blood concentration of PBDEs was approximately 81 ng/g lipid. The average PBDE concentration of males was significantly higher than females, using a 95% confidence level. In addition, PBDEs detected in human blood ranged approximately from 0.05 to 3676 ng/g lipid, with the highest concentrations found in black males. Also, a logistic regression analysis is conducted to determine whether an increase in background PBDE concentrations is a risk factor for obesity. Furthermore, the analyses of PBDEs are repeated for phthalates and polychlorinated Biphenyls for comparison. Finally, the measured concentrations of PBDEs are also compared to health outcome data known to show potential risk.
6

Leaching Potential of Metals and Brominated Flame Retardants in Obsolete Notebook Computers

Barnes, Otho 08 August 2009 (has links)
Due to the increasing use of electronic components and the accelerated rate in which these components become obsolete, there has been a dramatic increase of discarded electronic waste (E-waste). E-waste includes obsolete electronic products such as computers, scanners, cellular phones, etc. These electronic components are manufactured using a variety of hazardous materials. As these components are discarded, the toxic and hazardous substances may become mobile and could impact human health and the environment. The toxic substances of concern contained in E-waste include heavy metals and brominated flame retardants (BFRs). This study attempts to identify the leaching potential of BFRs and metals.
7

Giftfria förskolor i Nordmalings kommun : En inventering av förskolor med åtgärdsförslag för att möjliggöra en minskning av barns negativa hälsoeffekter till följd av kemikalieexponering

Norman, Belinda January 2016 (has links)
Humans are exposed to chemicals every day in our indoor environment. Chemicals have contributed to increased prosperity but also caused negative health effects. Children are vulnerable to chemicals because of their development and they breathe and drink more in relation to their body weight. That is why it’s important to reduce chemical exposure in environment for children. Preschools have a central role when it comes to materials and products that may pose a risk for exposure. The municipality has an important role to achieve a nontoxic environment which is based on a Swedish environmental quality goal (Non-toxic environment). This study is a part of the prioritized local environmental work in the municipal of Nordmaling. An inventory has been done to find out what type of chemicals that may expose children to harmful effects in preschools of Nordmaling. Electronic as a toy, soft and smelling toys, plastic around food and drinks, foam play pads were common products found during the inventory. This materials containing phthalates, brominated flame retardants, perfluorinated compounds, bisphenol A, lead and cadmium that can expose children through leaching into the indoor environment. A guidance have been constructed to achieve a non-toxic environment based on the results from the inventory in a cost effective way. The conclusion of the report is clear, identified problem areas can quickly be accomplished with small measures and low costs. Increased awareness of harmful substances and good routines for purchases and cleaning can further reduce the exposure to chemicals in the preschools.
8

Indoor emissions and fate of flame retardants : A modelling approach

Liagkouridis, Ioannis January 2016 (has links)
A significant number of consumer goods and building materials act as emission sources of flame retardants (FRs) in the indoor environment. As a result, FRs have become ubiquitous indoors raising concerns about human exposure and possible health implications. Once released indoors, FRs can escape to the outdoors where they can persist, be transported over long distances and present a threat to the environment. Despite the increasing number of studies reporting the occurrence of FRs in the indoor environment, the understanding of i) how and to what extent these chemicals are released from indoor sources, and ii) their subsequent fate indoors remains limited. The overarching objective of this thesis was to improve this understanding by assessing the indoor emissions and fate of FRs using a combination of multimedia modelling strategies and experimental/empirical approaches. Paper I identifies a number of knowledge gaps and limitations regarding indoor emissions and fate of FRs and the available modelling approaches. These include a limited understanding of the key emission mechanisms for low volatility FRs, uncertainties regarding indoor air/surface partitioning, poor characterization of dust and film dynamics and a significant lack of knowledge regarding indoor reaction/degradation processes. In Paper II we highlighted the serious scarcity in physicochemical property data for the alternative FRs and demonstrated the applicability of a simple QSPR technique for selecting reliable property estimates for chemical assessments. A modelling fate assessment indicated a strong partitioning to indoor surfaces and dust for most of the alternative FRs. Indications for POP (persistent organic pollutant)-like persistence and LRT (long-range transport) and bioaccumulative potential in the outdoor environment were also identified for many alternative FRs. Using an inverse modelling approach in Paper III we estimated 2 to 3 orders of magnitude higher emissions of organophosphate FRs (0.52 and 0.32 ng.h-1) than brominated FRs (0.083 μg.h-1 and 0.41 μg.h-1) in Norwegian households. An emission-to-dust signal was also identified for organophosphate FRs suggesting that direct migration to dust may be a key fate process indoors. No evidence of a direct source-to-dust transfer mechanism was seen in Paper IV where the chemical transfer between a product treated with an organophosphate FR and dust in direct contact was experimentally investigated. It was concluded though that direct contact between an FR source and dust can result in contamination hotspots indoors. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.</p>
9

Nanoporous Materials for Carbon Dioxide Separation and Storage

Varela Guerrero, Victor 2011 May 1900 (has links)
Global climate change is one of the most challenging problems that human beings are facing. The large anthropogenic emission of CO2 in the atmosphere is one of the major causes for the climate change. Coal-fired power plants are the single-largest anthropogenic emission sources globally, accounting for approximately one third of the total CO2 emissions. It is therefore necessary to reduce CO2 emission from coal-fired power plants. Current technologies for the post-combustion CO2 capture from flue gas streams can be broadly classified into the three categories: absorption, adsorption, and membrane processes. Despite challenges, CO2 capture by adsorption using solid sorbents and membranes offers opportunities for energy-efficient capture and storage of CO2. Nanoporous materials have attracted tremendous interest in research and development due to their potential in conventional applications such as catalysis, ion-exchange, and gas separation as well as in advanced applications such as sensors, delivery, and micro-devices. In the first part of this dissertation, we will study the synthesis of membranes using an emerging class of nanoporous materials, metal-organic frameworks (MOFs) for carbon dioxide (CO2) separations. Due to the unique chemistry of MOFs which is very different from that of zeolites, the techniques developed for the synthesis of zeolite membranes cannot be used directly. In order to overcome this challenge, a couple of novel techniques were developed: 1) "thermal seeding" for the secondary growth and 2) "surface modification" for the in situ growth. Membranes of HKUST-1 and ZIF-8, two of the most important MOFs, were prepared on porous α-alumina supports using thermal seeding and the surface modification techniques, respectively. The second part of this dissertation demonstrates a simple and commercially viable application of nanoporous materials (zeolite 5A and amine-functionalized mesoporus silica), storing CO2 as a micro-fire extinguishers in polymers. Materialist is observed that by dispersing these highly CO2-philic nanoporous materials in polymer matrices, the propagation of flame was greatly retarded and extinguished. This flame retarding behavior is attributed to the fact that CO2 released from the sorbents (zeolite 5A and mesoporous silica), blocks the flow of oxygen, therefore causing the fire to be effectively extinguished. Our results suggest that the binding strength of CO2 on sorbents play an important role. If the binding strength of CO2 is too low, CO2 releases too early, thereby ineffective in retarding the flame.
10

Effects of Four New Brominated Flame Retardants on Hepatic Messenger RNA Expression, In Vitro Toxicity and In Ovo Toxicity in the Domestic Chicken (Gallus gallus)

Egloff, Caroline 09 May 2011 (has links)
Brominated flame retardants (BFR) such as hexachlorocyclopentadienyl-dibromocyclooctane (HCDBCO), bis(2-ethylhexyl)tetrabromophthalate (BEHTBP), 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) and decabromodiphenylethane (DBDPE) are contaminants of environmental concern. These BFRs are replacement alternatives for some of the major production BFRs, which have been restricted from the marketplace due to their adverse health effects. Their presence in environmental matrices, including wild birds, suggests they should be tested for possible toxic effects. BFR alternatives have been detected in the eggs of colonial fish-eating birds, suggesting maternal transfer during ovogenesis and the potential for these chemicals to bioaccumulate through the food chain. However, information regarding the toxicity of HCDBCO, BEHTBP, BTBPE and DBDPE exposure in birds is lacking. This thesis consisted of a combined in vitro/in ovo approach to determine: 1) the concentration-dependent effects of these four BFR alternatives in chicken embryonic hepatocytes (CEH), and 2) the dose-dependent effects of HCDBCO and BTBPE in chicken embryos following injection into the air cell of eggs prior to incubation. Changes in the mRNA expression levels of genes previously found to be responsive to other BFRs were assessed in CEH and liver tissue, in addition to examining overt toxicity (i.e. cytotoxicity, pipping success). None of the BFRs tested were cytotoxic up to 60 µM HCDBCO, 60 µM BEHTBP, 1.4 µM BTBPE or 0.2 µM DBDPE in CEH. Injection doses up to 50 µg/g egg HCDBCO and 10 µg/g egg BTBPE had no effect on embryonic pipping success. The accumulation of HCDBCO and BTBPE was variable in liver and did not follow a linear uptake pattern with respect to injection dose, due in part to difficulties with the solubility of these chemicals in the dimethyl sulfoxide (DMSO) vehicle. In, CEH, HCDBCO caused a decrease in CYP1A4/5 mRNA at all concentrations tested, while CYP2H1 and CYP3A37 were induced only at 10 µM. In contrast, only TTR mRNA was down-regulated in hepatic tissue at all injection concentrations of HCDBCO. The highest concentration of BTBPE induced CYP1A4/5 mRNA to 115- and 18-fold in CEH, and 6.5- and 1.8-fold in liver tissue. In vitro and in ovo exposure to BTBPE caused a concentration-dependent decrease in DIO3 mRNA, while CYP3A37 was down-regulated 2-fold at 10 µg/g in liver tissue. In CEH, DBDPE induced CYP1A4/5 mRNA to a maximum of 29- and 59-fold at 0.2 µM, and increases in DIO1 mRNA and decreases in CYP3A37 mRNA were also observed. None of the gene targets were responsive to BEHTBP exposure in CEH. This is the first study to report on the toxicological and molecular effects of HCDBCO, BEHTBP, BTBPE and DBDPE in an avian species. Using this combined in vitro/in ovo approach has permitted the characterization of these four BFR alternatives by defining possible mechanisms of biological action in a model avian species, the chicken.

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